What Panorama Stitching Software do you use?

PTGUI is by far the best I have tried, way more accurate than Photoshop CS6.

PTGui also has the benefit of really using multiple threads, and tons of memory if you have it. When I first used PTGui it took 11 hours to render a monster pano I shot in 2006, and at the time it was the only software able to handle such a large task.

Now with version 9, it's able to take advantage of at least 12 threads, probably more, and more than 32GB of memory (I have 64GB), the same pano now completes in under 2 minutes.

Also the stitching accuracy has improved over time, back in 2006 there were some small errors, now even those don't occur. It's outstanding software.